proptnl - Delegates are allocated proportionally
WTA - Winner-Take-All
AP/CW - At-large delegates are proportional, Congressional District delegates are Winner-Take-All
AP/CU - At-large delegates are proportional, Congressional District delegates are unbound
AU/CW - At-large delegates are unbound, Congressional District delegates are Winner-Take-All
Conv - The delegation will be elected on the floor of the state convention based on stated
presidential preference.
Open - Anyone feom any Party or unaffiliated registartion can vote in either the primary or caucus.
Modified - Only registered Republicans and Registered Independent
or unafilated voters can vote in the primary or caucus.
Closed - Only registered Republicans can vote in the primary or caucus
* If any candidate receives more than 50% of the votes it becomes a WTA contest.
# If any candidate receives more than 66% of the votes it becomes a Winner-take-all contest.
1 The state, district or territory convention can vote to bind some or all of the delegates
3 This is simply a high-profile strawpoll. The real contest happens later.

N/A -
Caucus process can produce both pledged and unpledged convention delegates, depending on the party rules of the various states.
Some states follow with a state convention
In Pennsylvania each Republican delegate is allowed to support the candidate of their choice, irrespective of voting results in the GOP primary.
see Republican Party presidential primaries, 2012 - Wikipedia

 Penalties:
Several States were penalized 50% of their delegates, because they violated Republican National Committee (RNC) rules such as moving primary dates up prior to Super Tuesday.

 Missouri will hold a primary on Feb. 7th which will not count toward delegates, a caucus on March 17th will count.
Nebraska will do something similar on May 15 and July 14.
How it Works - (Delegates, Superdelegates, Open/Closed, Primary, Caucus)

Some of the rules are determined by the national committee for each party and some by state organizations.

How is the number of delegates per state determined?
There are 56 voting units; 50 states, which get all 4 categories of delegates (below), 5 Territories (Puerto Rico, Guam, American Samoa, U.S. Virgin Islands & Northern Marianas) and the District of Columbia, which only get base at-large and party delegates.
State delegate counts are reached based on a formula of:
a. Congressional Districts - 3 per district (435 districts) = 1,305;
b. Base at-large - 10 per state, 6 per territory = 560;
c. Party official delegates - 3 per state/territory) = 168;
(Includes 132 superdelegates)
d. Bonus delegates are given to states that elect a Republican Governor and for each Republican U.S. Senator that represents their state (1 [e.g. New York] dto 34 [Texas] per state) = 396.
2012 Totals Before penalty: 2,429 delegates
Source: White House 2012
See also Republican Delegate Allocation | TheGreenPapers.com

Terms:

Proportional = Delegates are handed out based upon the percentage of their total votes

Winner-Take-All = The winner takes all of the states delegates to the convention

Winner-Take-All (by distrcit) = Delegates are handed out by the congressional districts candidates win in

Open = Anyone from any Party or unaffiliated registartion can vote in either the primary or caucus

Modified = Only registered Republicans and Registered Independent or unafilated voters can vote in the primary or caucus

Closed = Only registered Republicans can vote in the primary or caucus

Primary = Primaries are similar to general elections. Voters cast secret ballots at polling places, and can come and go as they please.

Caucus = Caucus' require voters to get together face-to-face and discuss who to vote for. They can last 15 minutes or several hours.

Superdelegates
are party leaders and elected officials ("PLEOs"). All the superdelegates are free to support any candidate for the nomination.
For Republicans, in 2012, there are potentially 3 superdelegates in each state, consisting of the state chairman and two RNC committeemen/women. However, certain states either have no superdelegates or have them but whose votes are bound by the results of the state vote. In 2012, there are a total of 132 Republican superdelegates.

In some states, delegates are bound, or "pledged" to vote for the primary winner in voting at the national convention. In other states some or all delegates are "unpledged," and free to vote for any candidate they wish at the convention.

* Dec. 29 Insider Advantage excluded from Average calculation
 Romney was originally declared the winner 30,015 (24.55%) to 30,007 (24.54%),
but two weeks later on Jan. 18, the Iowa GOP said certified results showed Santorum was ahead by 34 votes, but no official winner was declared because votes from eight precincts were missing. See Fox News

Classification - Moderate - ConservativeWho's the Most Conservative GOP Contender? A Candidate Matrix - News - GOOD - August 13, 2011
"The candidates' matrix positions were determined by an algorithm of a one through five rating, five being the most conservative. The categories for fiscal issues were taxes, budget, corporation-friendliness, health care, and government programs. For social issues, they were abortion and sex, civil rights, war, environment, and immigration."

Nate Silver, who developed the chart, says,
"One dimension is obvious: we can classify the candidates from left to right, from relatively more moderate to relatively more conservative. But another dimension that is often salient in the primaries, and perhaps especially so for Republicans next year, is what we might think of as the insider/outsider axis: whether the candidate is viewed as part of the Republican establishment, or as a critic of it."

Speculated candidates, Palin, Huckabee, Daniels, Thune, Giuliani, Trump and Christie never entered the campaign.
As of Dec. 4, 2011, Pawlenty and Cain had withdrawn or suspended their campaigns.

The area of each candidate's circle is proportional to their perceived likelihood of winning the nomination, according to the Intrade betting market.
The color of each circle reflects the region the candidate is from: blue for the Northeast, red for the South, green for the Midwest, and yellow for the West.

Silver comments, "Gingrich is a difficult case, a former Speaker of the House (it's hard to get more establishment than that), led the 1994 Republican Revolution, but has more recently aligned himself with Tea Party groups."

As of Dec. 5, intrade says there is a 30% change that Palin, Trump, Bloomberg, Paul OR Bachmann will run for President as Independent or 3rd party candidate.

Ratings for each candidate on the issues that are important to conservatives: the economy and jobs, gun rights, low taxes, runaway government spending and small government, abortion, foreign policy, the war on terror, national defense, stopping the onslaught of illegal aliens, and border security. The highest score is a 10, the lowest a 1.

We have assigned all candidates a Patriot Rating based on comprehensive analysis of many factors. Among these are their record, experience, capability, character, leadership qualifications and, of course, a demonstrated ability to abide by their prescribed oath "to support and defend" our Constitution. We evaluate their record of defending Essential Liberty, and their support for restoration of constitutional limits upon government -- including the judiciary -- the promotion of free enterprise, national defense and traditional American values. The rating is from 1 to 10, the higher the better.
We do not rate candidates on "electability."